Directions When you have selected your answer to each question blacken the corre

Question

Directions When you have selected your answer to each question blacken the corresponding space on the pencil. Make a heavy, full mark but not stray mark. If you decide to change an answer., erase the unwanted Make no marks on the test booklet. Do all calculations on scratch paper provided by your instructions. There is only one correct answer to each question. Any questions for which more than one response has been blackened will be continued. Your score is based on the number of questions you answer correctly. It is to your advantage to answer every question. For the reaction A + 2B rightarrow 2C + D, what is the order of the above reaction with respect to [B]? 1 1.5 2 3 Which plot shows a first-order reaction with respect to reactant A? The reaction 2NO rightarrow N_2 + O_2, has a rate constant of 3.6 times 10^-2M^-1 s^-1. When [NO] = 2.8 times 10^-3 M, what is the rate of change in Ms^-1 for N_2? 5.6 times 10^-7 1.0 times 10^-4 2.8 times 10^-7 5.0 times 10^-3 Atom A, represented by a circle, dimerizes to form A_2 molecules 2A(g) rightarrow A_2(g) What is the initial rate of formation of A_2 in molecules per second? 10 15 20 40 The decomposition of N_3O_4 is studied at 20 degree C and at 80 degree C. Which statement explains why the rate at 80 degree C is greater than at 20 degree C? The activation energy is lower at 80 degree C. The activation energy is higher at 80 degree C The concentration of a gas increases with increasing temperature. The number of molecules with enough energy to react is greater at 80 degree C. Compound A decomposes to form compound B. When 1/[A] is plotted versus time, a straight line with slope of 0.53 M^-1 min^-1 results. What is the rate law rate = 0.53 M^-1 min^-1 rate = 0.53 M^-1 min^-1 rate = 0.53 M^-1 min^-1[A]^2 more information is necessary. The rate law for the reaction A + B + C rightarrow D + E rate = k[A][B]^2. If the initial concentrations of A are doubled while all other conditions remain by what factor will the reaction rate change? 2 4 8 The reaction rate will not change In this reaction, I^- is consumed at a rate 2.5? What is the rate of formation of I_2 in M middot s? IO^-_3 + 5I^- + 6H' rightarrow 3I_2 + 3H_2O 0.25 1.5 2.5 For this two-step reaction sequence, identify the intermediate and catalyst. Step 1: H_2O_2 + Br^- rightarrow BrO^- + H_2O Step 2: H_2O_2 + BrO^- rightarrow Br^- + H_2O + O_2 Reaction intermediate Catalyst (A) Br^- BrO^- (B) BrO^- H_2O (C) BrO^- Br^- (D) H_2O_2 Br^-

Explanation / Answer

1) on decrease the concentration of B and keeping the concentration of A constant the rate of reaction decreases

The decrease in concentration of B = 0.019 / 0.048 = 0.4

the decrease in rate of reaction = 6.3 X 10^-6 / 1.6 X 10^-5 = 0.4

so the order with respect to B = 1

2) The rate law expression for first order is

lnA = lnA0 - Kt

so on plotting a graph between time and ln A we will get a straight line with negative slope

so answer: (A)

3) As per the unit of rate constant the order of reaction = 2 [Unit M-1s-1]

Rate = K [NO2]^2

Rate of reaction = 3.6 X 10^-2 [2.8 X 10^-3]^2 = 28.224 X 10^-8 = 2.8 X 10^-7

4) Initial concentration of A = 10

Final concentration of A = 4

Rate of formation = 1/2 X Change in concentration of A / Time = 10- 4 / 0.20 = 15

5) The activation energy is lower at 80 C

6) 1/[A] v/s time is a straight line so the order of reaction = 2

Rate = K [A]2 = 0.53[A]2

7) IF other conditions are kept constant then the rate of reaction will become double as the order with respect to [A] =1

8) The rate of consumption of I- = (5/3) Rate of formation of I2

Rate of formation of I2 = 3 X 2.5 / 5 = 1.5

9) Intermediate = BrO-

Catalyst = Br-

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